Network Working Group J. Schiller
Request for Comments: 3365 Massachusetts Institute of Technology
BCP: 61 August 2002
Category: Best Current Practice
Strong Security Requirements for
Internet Engineering Task Force Standard Protocols
Status of this Memo
This document specifies an Internet Best Current Practices for the
Internet Community, and requests discussion and suggestions for
improvements. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
It is the consensus of the IETF that IETF standard protocols MUST
make use of appropriate strong security mechanisms. This document
describes the history and rationale for this doctrine and establishes
this doctrine as a best current practice.
Table of Contents
1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Security Services . . . . . . . . . . . . . . . . . . . . . . 2
4. The Properties of the Internet. . . . . . . . . . . . . . . . 3
5. IETF Security Technology. . . . . . . . . . . . . . . . . . . 3
6. The Danvers Doctrine. . . . . . . . . . . . . . . . . . . . . 4
7. MUST is for Implementors. . . . . . . . . . . . . . . . . . . 5
8. Is Encryption a MUST? . . . . . . . . . . . . . . . . . . . . 5
9. Crypto Seems to Have a Bad Name . . . . . . . . . . . . . . . 6
10. Security Considerations . . . . . . . . . . . . . . . . . . . 6
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
13. Author's Address . . . . . . . . . . . . . . . . . . . . . . 7
14. Full Copyright Statement . . . . . . . . . . . . . . . . . . 8
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1. Introduction
The purpose of this document is to document the IETF consensus on
security requirements for protocols as well as to provide the
background and motivation for them.
The Internet is a global network of independently managed networks
and hosts. As such there is no central authority responsible for the
operation of the network. There is no central authority responsible
for the provision of security across the network either.
Security needs to be provided end-to-end or host to host. The IETF's
security role is to ensure that IETF standard protocols have the
necessary features to provide appropriate security for the
application as it may be used across the Internet. Mandatory to
implement mechanisms should provide adequate security to protect
sensitive business applications.
2. Terminology
Although we are not defining a protocol standard in this document we
will use the terms MUST, MAY, SHOULD and friends in the ways defined
by [RFC2119].
3. Security Services
[RFC2828] provides a comprehensive listing of internetwork security
services and their definitions. Here are three essential
definitions:
* Authentication service: A security service that verifies an
identity claimed by or for an entity, be it a process, computer
system, or person. At the internetwork layer, this includes
verifying that a datagram came from where it purports to originate.
At the application layer, this includes verifying that the entity
performing an operation is who it claims to be.
* Data confidentiality service: A security service that protects
data against unauthorized disclosure to unauthorized individuals or
processes. (Internet Standards Documents SHOULD NOT use "data
confidentiality" as a synonym for "privacy", which is a different
concept. Privacy refers to the right of an entity, normally a
person, acting in its own behalf, to determine the degree to which
it will interact with its environment, including the degree to
which the entity is willing to share information about itself with
others.)
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* Data integrity service: A security service that protects against
unauthorized changes to data, including both intentional change
(including destruction) and accidental change (including loss), by
ensuring that changes to data are detectable.
4. Some Properties of the Internet
As mentioned earlier, the Internet provides no inherent security.
Enclaves of networking exist where users believe that security is
provided by the environment itself. An example would be a company
network not connected to the global Internet.
One might imagine that protocols designed to operate in such an
enclave would not require any security services, as the security is
provided by the environment.
History has shown that applications that operate using the TCP/IP
Protocol Suite wind up being used over the Internet. This is true
even when the original application was not envisioned to be used in a
"wide area" Internet environment. If an application isn't designed
to provide security, users of the application discover that they are
vulnerable to attack.
5. IETF Security Technology
The IETF has several security protocols and standards. IP Security
(IPsec [RFC2411]), Transport Layer Security (TLS [RFC2246]) are two
well known protocols. Simple Authentication and Security Layer (SASL
[RFC2222] and the Generic Security Service Application Programming
Interface (GSSAPI [RFC2743]) provide services within the context of a
"host" protocol. They can be viewed as "toolkits" to use within
another protocol.
One of the critical choices that a protocol designer must make is
whether to make use of one of the existing protocols, engineer their
own protocol to use one of the standard tools or do something
completely different.
There is no one correct answer for all protocols and designers really
need to look at the threats to their own protocol and design
appropriate counter-measures. The purpose of the "Security
Considerations" Section required to be present in an RFC on the
Internet Standards Track is to provide a place for protocol designers
to document the threats and explain the logic to their security
design.
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6. The Danvers Doctrine
At the 32cd IETF held in Danvers, Massachusetts during April of 1995
the IESG asked the plenary for a consensus on the strength of
security that should be provided by IETF standards. Although the
immediate issue before the IETF was whether or not to support
"export" grade security (which is to say weak security) in standards
the question raised the generic issue of security in general.
The overwhelming consensus was that the IETF should standardize on
the use of the best security available, regardless of national
policies. This consensus is often referred to as the "Danvers
Doctrine".
Over time we have extended the interpretation of the Danvers Doctrine
to imply that all IETF protocols should operate securely. How can
one argue against this?
Since 1995 the Internet has increasingly come under attack from
various malicious actors. In 2000 significant press coverage was
devoted to Distributed Denial of Service attacks. However many of
these attacks were launched by first compromising an Internet
connected computer system. Usually many systems are compromised in
order to launch a significant distributed attack.
A conclusion we can draw from all of this is that if we fail to
provide secure protocols, then the Internet will become less useful
in providing an international communications infrastructure, which
appears to be its destiny.
One of the continuing arguments we hear against building security
into protocols is the argument that a given protocol is intended only
for use in "protected" environments where security will not be an
issue.
However it is very hard to predict how a protocol will be used in the
future. What may be intended only for a restricted environment may
well wind up being deployed in the global Internet. We cannot wait
until that point to "fix" security problems. By the time we realize
this deployment, it is too late.
The solution is that we MUST implement strong security in all
protocols to provide for the all too frequent day when the protocol
comes into widespread use in the global Internet.
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7. MUST is for Implementors
We often say that Security is a MUST implement. It is worth noting
that there is a significant different between MUST implement and MUST
use.
As mentioned earlier, some protocols may be deployed in secure
enclaves for which security isn't an issue and security protocol
processing may add a significant performance degradation. Therefore
it is completely reasonable for security features to be an option
that the end user of the protocol may choose to disable. Note that
we are using a fuzzy definition of "end user" here. We mean not only
the ultimate end user, but any deployer of a technology, which may be
an entire enterprise.
However security must be a MUST IMPLEMENT so that end users will have
the option of enabling it when the situation calls for it.
8. Is Encryption a MUST?
Not necessarily. However we need to be a bit more precise here.
Exactly what security services are appropriate for a given protocol
depends heavily on the application it is implementing. Many people
assume that encryption means confidentiality. In other words the
encryption of the content of protocol messages.
However there are many applications where confidentiality is not a
requirement, but authentication and integrity are.
One example might be in a building control application where we are
using IP technology to operate heat and vent controls. There is
likely no requirement to protect the confidentiality of messages that
instruct heat vents to open and close. However authentication and
integrity are likely important if we are to protect the building from
a malicious actor raising or lowering the temperature at will.
Yet we often require cryptographic technology to implement
authentication and integrity of protocol messages. So if the
question is "MUST we implement confidentiality?" the answer will be
"depends". However if the question is "MUST we make use of
cryptographic technology?" the answer is "likely".
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9. Crypto Seems to Have a Bad Name
The mention of cryptographic technology in many IETF forums causes
eyes to glaze over and resistance to increase.
Many people seem to associate the word "cryptography" with concerns
such as export control and performance. Some just plain do not
understand it and therefore shy away from its use. However many of
these concerns are unfounded.
Today export control, at least from most of the developed world, is
becoming less of a concern. And even where it is a concern, the
concern is not over cryptography itself but in its use in providing
confidentiality.
There are performance issues when you make use of cryptographic
technology. However we pride ourselves in the IETF as being
engineers. It is an engineering exercise to figure out the
appropriate way to make use of cryptographic technology so as to
eliminate or at least minimize the impact of using cryptography
within a given protocol.
Finally, as to understanding cryptography, you don't have to. In
other words, you do not need to become a cryptographer in order to
effectively make use of cryptographic technology. Instead you make
use of existing well understood ciphers and cipher suites to solve
the engineering problem you face.
One of the goals that we have in the Security Area of the IETF is to
come up with guides so that protocol implementers can choose
appropriate technology without having to understand the minutiae.
10. Security Considerations
This document is about the IETF's requirement that security be
considered in the implementation of protocols. Therefore it is
entirely about security!
11. Acknowledgements
The author would like to acknowledge the participation of the
Security Area Advisory Group and in particular Rob Shirey, Ran
Atkinson, Steve Bellovin, Marc Blanchet, Steve Kent, Randy Bush, Dave
Crocker, Stephen Farrell, Paul Hoffman, Russ Housley, Christian
Huitema, Melinda Shore, Adam Shostack and Kurt D. Zeilenga.
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12. References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2222] Myers, J., "Simple Authentication and Security Layer
(SASL)", RFC 2222, October 1997.
[RFC2411] Thayer, R., Doraswamy, N. and R. Glenn, "IP Security
Document Roadmap", RFC 2411, November 1998.
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
[RFC2743] Linn, J., "Generic Security Service Application Program
Interface Version 2, Update 1.", RFC 2743, January 2000.
[RFC2828] Shirey, R., "Internet Security Glossary", FYI 36, RFC 2828,
May 2000.
13. Author's Address
Jeffrey I. Schiller
MIT Room W92-190
77 Massachusetts Avenue
Cambridge, MA 02139-4307
USA
Phone: +1 (617) 253-8400
EMail: jis@mit.edu
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RFC 3365 Encryption Security Requirements August 2002
14. Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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